Arylpyrrole carbonitrile compounds and derivatives thereof are highly effective insecticidal, acaricidal and nematicidal agents. In particular 2-aryl-5-trifluoromethylpyrrole-3-carbonitrile compounds and their derivatives have been found to have a broad spectrum of activity at very low rates of application with effectiveness against resistant species. Methods to prepare said pyrrole compounds on a manufacturing scale include the 1,3-dipolar cycloaddition of the appropriate 3-oxazolin-5-one with 2-chloroacrylonitrile described in U.S. Pat. No. 5,030,735.
Methods known in the art to prepare 3-oxazolin-5-one compounds from glycine starting materials require either a 2 step synthesis which includes at least one equivalent of base for the first step amide formation and at least a second equivalent of base and/or an excess of dehydrating reagent such as an anhydride for the second step ring closure or an excess of an anhydride which acts as both an acylating agent and dehydrating agent to give the ring closed product in a single step. Both of these approaches require at least one equivalent of an acid scavenger for the initial amide formation and further may call for excesses of reagents which are known to be corrosive and hazardous.
It is an object of this invention to provide an effective single step procedure to prepare 4-aryl-2-perfluoroalkyl-3-oxazolin-5-one from aryl glycine which avoids the use of an additional acid scavenger (i.e., a second equivalent of base) and further eliminates the need for excessive amounts of potentially hazardous and corrosive acylating reagent.
It is a further object of this invention to provide an efficient and convenient source of a key intermediate in the production of arylpyrrole carbonitrile pesticidal agents.